This invention concerns circular knitting machines, and refers in particular to the construction of tubular knitted articles with one closed end, such as socks and like, on said knitting machines.
In the field of the technique taken into consideration here, work procedures and devices have already been proposed and at present are in particular demand, which enable one end of a tubular knitted product to be closed automatically, such as the toe of a sock or like, directly on or on board the knitting machine and however without having to finish the product when off the machine.
When carried out on a circular machine, the knitting of a sock or stocking usually finishes in the toe portion with at least the last row of stitches which remain on the needles of the cylinder, evidently in a circular formation. In order to be able to close the sock toe, the two opposite half circles of tubular knitted fabric on a level with the last rows of knitting must be brought together, forming two edges that touch and which can be joined either by linking or sewing.
One of the methods used at present in performing this operation consists in transferring the knitting from the needles of the cylinder to hooks placed on a dial above the cylinder. The dial is formed by two half disks which can turn on an intermediate diametrical axis so as to move the two end edges of the sock together, which are then joined to form the closed toe.
Another method consists in removing the knitting from the needles of the cylinder using means of transfer onto two half crescents, which on turning overlap, approaching to each other the semicircular opposite ends of the same row of knitting at the end of the knitted article.
A further method envisages transforming a row of circular knitting at the end of the product into two straight segments through the deformation of an annular device holding pick-up needles or hooks. For this purpose the annular device has several articulated sectors side by side, which, when opened, position themselves according to a circumference to receive the tubular knitted fabric from the cylinder needles and when made to approach each other form two almost parallel, facing edges, positioned according to two rectilinear close lengths.
In concrete, on finishing the knitting of a sock with the needles on the cylinder of a circular machine, using this last method, the following steps are carried out in sequence:
position the needles on the cylinder at a certain level; move towards the cylinder top the picking-up devices placed on a plurality of sectors arranged in a opened circular position;
turn the product upside down, drawing it towards the top;
transfer the end parts of the knitted product from the needles of the cylinder to the pick-up devices on said opened sectors;
place the sectors with the pick-up devices close to each other and positioned in two parallel rows so that the knitted fabric forms two close straight sections,
move the pick-up devices into a stitching area distant from the cylinder of the machine; and
sew the two straight sections of knitting together by a sewing machine so as to close the end, that is the toe, of the product.
Consequently, all the operations to be carried out between the end of the knitting of the sock to final sewing of its end, the toe, take place on board the machine above the cylinder, with a machine cover open, with operating times which are totalised while the machine remains inoperative in that it in the knitting mode.
In particular, the turning upside down of the product chronologically anticipates the pick-up or transfer phase of the knitting from the needles of the cylinder to the pick-up devices, and the aligning and approaching phase of the sectors in two rows is carried out before moving the pick-up devices with the sock turned upside down towards the sewing zone.
This sequence of operating phases is however the cause of important problems which involve both the construction of the machine and the productivity of the same. On the one hand, for example, the machine must be equipped so that machine cover and dial have a wide opening which in itself negatively influences the disposition and stress of the threads. On the other hand, and even more to its disadvantage, the times required for the operating phases carried out on board the machine severely penalise performance.
One object of this invention is to remedy the problems and drawbacks complained about above, by carrying out, at least the turning upside down operation of the product and the approach of the ends of the fabric to be joined together, off the machine.
Another object of the invention is to provide a simplified circular sock knitting machine which, although equipped with means for picking-up and closing one end of the product, still maintains its high production, in that it can start production of a new item while the previous item is being handled and placed in the condition to have the toe re-knitted or sewn.
In other terms, at least the operating times of the turning upside down and closing of a previously knitted article are limited, therefore included, in the time required to knit the following or a new item.
These objects and inherent advantages are achieved by a method of knitting tubular fabric article with one closed end, such as socks with closed toe, on a circular knitting machine equipped with pick-up means in the form of needles or hooks associated with a device for turning the item over so that the bottom is uppermost, and where the pick-up means are positioned on linked supporting sectors, which are able to move from an annular position corresponding to the needles cylinder of the machine and a linear position on two parallel facing rows and which can be moved above and at a distance from the needles cylinder to a sewing area, comprising the step of:
opening, on termination of the knitting of the item, a cover of the machine and moving the supporting sectors of the pick-up means into a circular configuration above the cylinder with needles,
transferring the knitted item to the height of at least the last row of knitting from the needles of the cylinder to said pick-up means on said supporting sectors in a circular configuration,
moving the knitted item away from the cylinder towards the sewing area, while it is held by said pick-up means on the supporting sectors in a circular configuration,
resetting and restarting the machine to start a new item,
turning the knitted item over so that the bottom is uppermost through said pick-up devices in a circular configuration,
moving the supporting sectors to meet each other in a linear position along two lines so as to place the two opposite ends of knitted fabric to form a straight line and in contact with each other on said pick-up means, and
joining the two ends of the knitted fabric now in contact, either by sewing or linking.